Reporter: We are on the streets of new york city with models abby smith and kristin garofalo. Abc news has hired them because pe trainer ryan hugh- come with me. Reporter: -- Is confessing something about gyms we had to see to believe. Most of the time at these large corporate gyms you're going to get a better rate if you're thin and attractive rather than overweight. Reporter: Ryan's skinny on gyms, if you're fit and thin like kristin, you're going to get a better deal at the gym than heavier people like abby. Why? Because ryan says trainers think hot chicks boost their business. Having an attractive person on the floor is always a win-win. Reporter: At our first stop, abby thinks she got a great deal from an expanding national fitness chain. I just got an email. He said it was great meeting me and he's going to set me up with my complimentary guided workout. Reporter: But kristin is about to open abby's eyes to how gym's really do business. What my sales advisor said to me was that he can waive the $200 initiation fee. Oh. Reporter: It's a $200 savings abby is never even offered. Could it be a fluke? We drive abby and kristin a few blocks away. How'd it go? It went well. He said my monthly rate is $152. Different? Yeah! Reporter: Yeah, different. This time, kristin gets a $276 break on her annual membership -- the numbers don't even compare. Why wouldn't you offer the exact same rate to everybody that comes in your gym? That's ridiculous to me! Reporter: But if you think it couldn't get any worse -- it does. We head downtown -- to one of new york's boutique gyms and this time, there's no questioning why kristin gets the better deal. Okay, I got "the model's discount." Reporter: That so-called "model's discount" is a whopping $706 a year savings for kristin. Get out! Am I surprised, not at all. This kinda thing happens all the time. If you're going to bring five, ten people into this gym by just coming in and work out and looking good, then they are gonna bring you into the gym. Not bad, unless you're plus-sized abby. In total, we went to four gyms -- three of them national chains -- and the results were always the same. I never would have expected it. I never would have. Reporter: And ryan says women like abby should expect something else -- high pressure sales tactics to play on her insecurities and a "sell, sell, sell" mentality. Reporter: So are the gyms looking for easy money? Membership is huge, and then of course, selling a personal trainer. Reporter: Remember that e-mail abby got just minutes after inquiring about a membership? What you don't know is the gym offered to waive her initiation fee. Reporter: But? But, I had to sign up for some training sessions which were $100 apiece. Reporter: You had to? In order to get the initiation fee waived, yeah. Reporter: Ryan says the name of the game is signing folks up for long-term, upfront contracts with the anticipation those new members will never clock a single burned calorie on the treadmill. Two years down the road you are getting with a gym membership and you have never gone once. Reporter: Have you met or come across trainers who were frauds? I am sure there are trainers out there that are probably doing this strictly to make a buck. Getting a little pumped there, huh? Reporter: What do you get for your money? I recently worked out with ryan in this south florida gym. He put me through the ringer. And confessed something you won't want to hear. Ryan admits, he, and other trainers like him, secretly enjoy watching us sweat and suffer. Have you ever had anybody weep on you? Any crying? Maybe not some crying, but a couple of throw-ups. Reporter: Really? Uh, people who toss their cookies in the trash can a little bit, yeah. Reporter: That's gotta make you feel great. I will admit, there is a small bit of satisfaction that you get. Out of making a client puke. It doesn't happen all of the time, but when do you, it's kind of an internal, "yes!" Reporter: But ryan's about to reveal the biggest secret of all? So you wanna know what goes on behind these muscles? Reporter: Wanna look like this? Ryan says you're never going to unless you quit day job. Ryan's regimen borders on religion. He works out every day -- sometimes twice a day -- three hours or more. His diet is not only rigorous, but monastic. So ryan, when was the last time you had a beer? It's been a couple of years for a beer. Reporter: It's that whole cult of fitness and "looks-ism" that has sople screaming "enough!" Every single day, people get scared to go to the gym. People are afraid of being judged. People are afraid of getting charged too much. Reporter: At downsize fitness in chicago, justin hazlett now only sells gym memberships to clients who are 50 pounds overweight or heavier. Women like abby smith. She would be our next client. And this one, she'd be shown the door. Reporter: There's no "model discount" for kristin here. Skinny clients are banned from joining this gym -- and for good reason. I felt like in the gyms that I've been to before I've always been discriminated against just because of my size, for how much I weigh. Reporter: Back in new york city, abby smith and kristin garafolo are still shaking their heads over that jaw dropping $706 "model's discount." I want to go back into the gim gym with abby and go "hey, listen, this was my rate, and this is gonna be her rate too! Let me speak to your gm! Reporter: And, so we did. We were greeted by the general manager who insisted at his gym there is no price scale-no "wiggle room" for his 1,400 members. We never change our pricing. Reporter: How can that be? That's just something that we never compromise. We're a luxury brand, we don't discount our pricing. Reporter: What if I told you that we actually had two people come in here and they got vastly different prices. I'd be very surprised to hear that. Reporter: Really? Yes? Do you recognize either of these two ladies? He doesn't recognize either abby or kristin, but quickly begins to backpedal on that "one-size-fits-all" membership pricing policy. Is there something called a "model's discount?" Uh, not -- there are partnerships that we have with businesses. She's probably part of a modeling agency we have a partnership. Reporter: No, I don't think so. How does this work? Do you pay by the pound? I mean she's also a model. If she's heavier, she pays more? We don't create deals on the fly for how someone looks. Never. Reporter: The salesperson who saw this person automatically assumed that she was a model. The salesperson that saw this person did not. Well -- that was a misjudgment. Reporter: All right, so abby can come here if she chooses and get the same deal? Correct. Well that's interesting. That's nice. Reporter: Was there anything that really surprised you about this experience? I still don't want to believe it, really. I'd like to think that most places are pretty fair, but i guess that's just naive of me to think that. Next -- hey!

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